From: John Ogness <john.ogness@linutronix.de>
To: Helge Deller <deller@gmx.de>, Petr Mladek <pmladek@suse.com>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>,
Steven Rostedt <rostedt@goodmis.org>,
Thomas Gleixner <tglx@linutronix.de>,
linux-kernel@vger.kernel.org,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Jiri Slaby <jirislaby@kernel.org>,
"Paul E. McKenney" <paulmck@kernel.org>,
Frederic Weisbecker <frederic@kernel.org>,
Neeraj Upadhyay <quic_neeraju@quicinc.com>,
Josh Triplett <josh@joshtriplett.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Lai Jiangshan <jiangshanlai@gmail.com>,
Joel Fernandes <joel@joelfernandes.org>,
Kees Cook <keescook@chromium.org>,
Andrew Morton <akpm@linux-foundation.org>,
Luis Chamberlain <mcgrof@kernel.org>,
Wei Liu <wei.liu@kernel.org>, Xiaoming Ni <nixiaoming@huawei.com>,
Peter Zijlstra <peterz@infradead.org>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Marco Elver <elver@google.com>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Daniel Lezcano <daniel.lezcano@linaro.org>,
Shawn Guo <shawn.guo@linaro.org>,
Dmitry Torokhov <dmitry.torokhov@gmail.com>,
Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Phil Auld <pauld@redhat.com>, Juri Lelli <juri.lelli@redhat.com>,
Wang Qing <wangqing@vivo.com>,
rcu@vger.kernel.org
Subject: Re: [PATCH printk v2 09/12] printk: add functions to prefer direct printing
Date: Thu, 07 Apr 2022 22:10:19 +0206 [thread overview]
Message-ID: <878rsgvews.fsf@jogness.linutronix.de> (raw)
In-Reply-To: <7fc5853e-dbe6-c2d2-2130-003e3b9777bc@gmx.de>
On 2022-04-07, Helge Deller <deller@gmx.de> wrote:
> In my case - while I debug low-level kernel code - I then just need to
> use pr_warn() or pr_emerg() and get it printed non-threadened. That's
> sufficient for me.
Actually, no. The loglevel does not determine if a message is direct
printed or not. By "warn" I was referring to WARN_ON(condition).
If you are debugging low-level kernel code, you usually will _want_
threaded printing. The timestamps match the printk() call, so you will
get accurate logs. And the runtime performance of your low-level kernel
code will not be significantly affected by the printk() call.
If for some reason you really want non-threaded printing, the patch we
are discussing creates new functions to manually activate it:
printk_prefer_direct_enter();
pr_info("debugging\n");
printk_prefer_direct_exit();
But then your pr_info() will cause significant latencies. The timestamp
would be the same, with or without direct printing.
John
next prev parent reply other threads:[~2022-04-07 20:34 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-05 13:25 [PATCH printk v2 00/12] implement threaded console printing John Ogness
2022-04-05 13:25 ` [PATCH printk v2 01/12] printk: rename cpulock functions John Ogness
2022-04-06 9:07 ` Petr Mladek
2022-04-05 13:25 ` [PATCH printk v2 02/12] printk: cpu sync always disable interrupts John Ogness
2022-04-05 13:25 ` [PATCH printk v2 03/12] printk: get caller_id/timestamp after migration disable John Ogness
2022-04-05 13:25 ` [PATCH printk v2 04/12] printk: call boot_delay_msec() in printk_delay() John Ogness
2022-04-05 13:25 ` [PATCH printk v2 05/12] printk: add macro for console detail messages John Ogness
2022-04-06 10:31 ` Petr Mladek
2022-04-05 13:25 ` [PATCH printk v2 06/12] printk: refactor and rework printing logic John Ogness
2022-04-06 14:02 ` Petr Mladek
2022-04-05 13:25 ` [PATCH printk v2 07/12] printk: move buffer definitions into console_emit_next_record() caller John Ogness
2022-04-06 14:40 ` Petr Mladek
2022-04-05 13:25 ` [PATCH printk v2 08/12] printk: add pr_flush() John Ogness
2022-04-06 15:17 ` Petr Mladek
2022-04-08 18:57 ` John Ogness
2022-04-05 13:25 ` [PATCH printk v2 09/12] printk: add functions to prefer direct printing John Ogness
2022-04-07 9:56 ` Petr Mladek
2022-04-07 13:35 ` Helge Deller
2022-04-07 14:35 ` John Ogness
2022-04-07 19:36 ` Helge Deller
2022-04-07 20:04 ` John Ogness [this message]
2022-04-07 20:20 ` Helge Deller
2022-04-11 12:50 ` Petr Mladek
2022-04-09 15:57 ` Paul E. McKenney
2022-04-05 13:25 ` [PATCH printk v2 10/12] printk: add kthread console printers John Ogness
2022-04-07 16:43 ` start/stop: was: " Petr Mladek
2022-04-07 16:49 ` console_is_usable() check: " Petr Mladek
2022-04-07 16:53 ` wake_up_klogd(): " Petr Mladek
2022-04-07 16:56 ` console_flush_all(): was: : was " Petr Mladek
2022-04-05 13:25 ` [PATCH printk v2 11/12] printk: extend console_lock for proper kthread support John Ogness
2022-04-08 13:45 ` guarantee forward progress: was: " Petr Mladek
2022-04-08 20:17 ` John Ogness
2022-04-11 10:45 ` Petr Mladek
2022-04-08 13:52 ` register_console: " Petr Mladek
2022-04-05 13:25 ` [PATCH printk v2 12/12] printk: remove @console_locked John Ogness
2022-04-05 15:03 ` [PATCH printk v2 00/12] implement threaded console printing Andy Shevchenko
2022-04-05 21:24 ` John Ogness
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